This invention generally relates to a plural component dispensing apparatus adapted to mix and dispense multiple components therefrom, and a mixing nozzle assembly for use with dispensing apparatus of this type. More specifically, the invention relates to a dispensing device for forming and dispensing a product by mixing a plurality of chemically reactive components, the device including a replaceable mixing nozzle which completely isolates and separates the reactants from the dispenser body and allows the components to be more effectively mixed to provide better results and avoid problems associated with such apparatus.
In a variety of applications, it is desirable to mix a plurality of chemically reactive materials with one another, which may then be dispensed from a suitable dispensing apparatus. As an example, in polyurethane foam systems, a plurality of components are mixed together to form a polyester, polyurea, or polyether resin foam product. In polyurethane foam systems, the plural components to be mixed may comprise an isocyanate and polyol or other catalyst, each of which is generally stable and will stay in a liquid state for an extended period of time. Upon mixing of these components in the proper amount and in a thorough manner, a chemical reaction will cause polymerization of the components. In such resin blends, a blowing agent may be used to cause the reactive polyurethane to foam, cure and cross-link to form a solid material. Such materials are utilized as industrial foams for packaging, insulation, in the shaping and coating of articles or other uses. The requirement for mixing the components and thereafter dispensing the formed product has led to the design of a variety of dispensing apparatus adapted to mix plural components. In the design of dispensing apparatus utilized to mix plural components in this manner, the hardening of the mixed components within the dispensing apparatus may clog or block the dispensing passages and ports of the apparatus such that the dispensing device will be rendered inoperative. Conventionally, the dispensing apparatus may be cleaned by the use of solvents introduced into the device to wash out the individual components as well as the hardened resin material formed upon mixing. The use of such solvents is undesirable as the evaporation of the solvents may result in condensation of moisture which will interfere with the chemical reaction and may affect the quality of the formed product such as a polyurethane foam. Other drawbacks of such devices include the inability to properly meter the separate components and inadequate mixing of the components within the apparatus.
Regarding the discussion of solvents and the problems associated with solvent cleaning dispensers:
Solvents present an environmental disposal problem PA0 Solvents present a worker safety problem PA0 There is no universal solvent suitable for cured urethane PA0 Solvents add cost to the production PA0 RIM Technology requires very high mixing pressures not attainable in portable foam kit systems. PA0 RIM Technology requires elaborate machined high pressure mixing heads that operate off hydraulic pressure in order to function reliably. PA0 RIM Technology requires extensive maintenance. PA0 RIM Technology is very expensive.
Another technology used that has evolved to replace solvent flush technology is Reaction Injection Molding (RIM) in this method the materials are separately entered into a mixing chamber that is mechanically cleaned by a plunger which mechanically moves through the bore after the reaction to displace the reactants and clean the walls of the mixing chamber. This technology is widely practiced in the mass production of urethane plastic parts such as the automotive or shoe sole industries. The use of this technology is not desirable in the market intended for the new dispenser because:
A variety of prior art devices have been developed for mixing and dispensing of chemically reactive components In U.S Pat. No. 4,427,153, a plural component dispensing gun is disclosed which includes a spray gun nozzle having a one piece mixing chamber with axially displaced inlets stated to provide better mixing and having a sealing arrangement to prevent leakage of the separate components from the spray nozzle. In U.S. Pat. No. 4,023,733, a foam dispensing gun is disclosed as having a mixing chamber with liquid entry ports, wherein one liquid entry port is spaced upstream from the other to prevent undesirable cross-feeding between the inlet ports. This construction is also stated to provide better mixing of the plural components. In U.S. Pat. No. 4,708,292, a dispensing apparatus is shown as having a mixing chamber within the nozzle thereof into which the plural materials are introduced by separate inlet ports. The liquid components enter the mixing nozzle at an angle such that the separate streams of liquid are directed toward one another for better mixing. Although the above apparatus as well as other prior art dispensing devices have attempted to overcome the deficiencies in properly mixing the reacting components to optimize the production of polyurethane foam or the like, such apparatus is still deficient in some respects such as in providing proper metering of the individual liquid components and ensuring proper mixing continuously to optimize the polymerization process without fouling the dispenser in the process.
A variety of dispensing devices have also been designed to remedy the possible hardening or setting up of the reactive components within the device which creates significant problems. In U.S. Pat. No. 4,399,930, a foam dispensing gun includes a disposable nozzle for mixing and dispensing separate fluid components. The foam dispensing gun is designed to be inoperative in the absence of a dispensing nozzle on the gun and allows the nozzle to be removed for reloading. In U.S. Pat. No. 4,262,847, a urethane foam gun is disclosed which includes dual plug valves for control of separate streams of the plural components and a second gun-mounted valve which controls a solvent flush for cleaning. It is again found that such designs have drawbacks in properly maintaining the dispensing device in an operative condition and avoiding the blockage of internal passageways and nozzle of the apparatus.